1. Field of the Invention
This invention relates to a floor cable used for a telephone cord or the like to be laid in an office room or like chamber, and also to a method of producing such floor cable.
2. Prior Art of the Invention
Telephone cords or the like cables in an office room are usually laid under the floor to keep the fine appearance of the room.
This cable laid under the floor includes much of the core wires and accordingly is required to branch off the core wires in the use. The branching of the core wires is carried out by ripping first the sheath, drawing out the desired wire and, if necessary, attaching a branch wiring box to the open portion of the cable. The easiness or the difficulty of the branching work is dependent on that of the sheath ripping and that of the drawing out of the core wire.
The ripping of the sheath for the branching of connecting of the cable is usually carried out using a knife or like tool. A part of the cable sheath is first cut slantly by a knife, and the edge point is forceably thrust into a narrow space between the sheath and the cable core to rip out the sheath. As this cutting work is invisible and carried out on intuition and delicate touch, an untrained worker other than a skilled worker often damages the cable core and gets hurt during cutting.
An improved cable structure which includes high strength designated as "rip cords" in the sheath for facilitating the ripping work has been proposed, but the ripping of such cable is not so easy as the sheath must be cut for drawing out the rip cords.
Another improved structure of the cable has been proposed to obtain slacks or surplusages of the core wires by twisting the core wires, but full slacks are not achieved due to the low twisting ratio.
In order to obtain further slacks in the core wires, a cable structure wherein the twisted or bundled core wires are rippled has been proposed, but such cable has the defect that the rippled core wires occupy much space in the sheath and the outer diameter of the cable becomes too large.